Method and Apparatus for Signal Scanning for Multimode Receiver

1. A method comprising: providing an input signal at an input to a receiver; controlling a bandwidth of the receiver to a predetermined wideband setting; for each of a plurality of frequency bands: at the receiver, processing the input signal with a mixer, an amplifier, and a filter, to generate a first processed signal, and generating a power spectral density of the first processed signal over said frequency band, to provide a frequency domain signal for said frequency band; reconstructing, based on the frequency domain signals corresponding to each frequency band in the plurality of frequency bands, a frequency domain representation of the processed signal over a reconstruction band having a bandwidth larger than the predetermined wideband setting; and identifying, based on the reconstructed frequency domain representation, a spectral component corresponding to at least one cellular telephony access mode.

2. The method of claim 1 , wherein determining the power spectral density of the first processed signal includes computing a fast Fourier transform of the first processed signal.

3. The method of claim 1 , wherein each band in the plurality of frequency bands has a bandwidth equal to the predetermined wideband setting.

4. The method of claim 1 , wherein spectral components corresponding to at least a first and a second cellular telephony access mode are detected, and the first mode is different from the second mode.

5. The method of claim 4 , wherein the first mode is a wideband mode and the second mode is a narrowband mode.

6. The method of claim 5 , wherein the first mode is an LTE mode and the second mode is a GSM mode.

7. The method of claim 1 , wherein the at least one cellular telephony access mode includes a wideband mode identified by detecting a plurality of contiguous frequency bins each corresponding to a power higher than a predetermined threshold.

8. The method of claim 1 , wherein the at least one cellular telephony access mode includes a narrowband mode identified by detecting a one or more power spectral density spikes, wherein each spike corresponds to a frequency bin having a power exceeding the power at respective neighboring bins by at least a predetermined threshold.

9. The method of claim 1 , further comprising identifying, based on the reconstructed frequency domain representation, a carrier-free band containing no spectral components corresponding to any cellular telephony access modes, wherein the carrier-free band is within the reconstruction band.

10. The method of claim 1 , wherein the bands in the plurality of frequency bands are contiguous bands.

11. The method of claim 1 , further comprising: configuring the receiver to a frequency band associated with one of the modes; processing the input signal with the mixer, the amplifier, and the filter after the configuring, to generate a second processed signal; measuring power or voltage of the second processed signal; and if the measured power or voltage exceeds a predetermined threshold, synchronizing the receiver to a base station based on the frequency band associated with said one mode.

12. The method of claim 1 , wherein the at least one cellular telephony access mode includes a plurality of modes, the method further comprising: assigning a priority to each mode in the plurality of modes; configuring the receiver to frequency bands associated with the respective modes based on the priority of each mode; for each mode in order of priority: processing the input signal with the mixer, the amplifier, and the filter after the configuring of the receiver to the corresponding frequency band, to generate a second processed signal corresponding to said mode; measuring power or voltage of the second processed signal; and if the measured power or voltage exceeds a predetermined threshold, synchronizing the receiver to a base station based on the frequency band associated with said mode.

13. The method of claim 12 , further comprising: identifying, based on the reconstructed frequency domain representation, a carrier-free band containing no spectral components corresponding to any cellular telephony access modes, wherein the carrier-free band is within the reconstruction band; assigning to said carrier-free band a priority lower than all the priorities assigned to the respective modes in the plurality of modes; configuring the receiver to said carrier-free band; processing the input signal with the mixer, the amplifier, and the filter after the configuring of the receiver to said carrier-free band, to generate a second processed signal corresponding to said carrier-free band; measuring power or voltage of said second processed signal corresponding to said carrier-free band; and if the measured power or voltage of said second processed signal corresponding to said carrier-free band exceeds said predetermined threshold, synchronizing the receiver to a base station corresponding to said carrier-free band.

14. A system comprising: a receiver including a mixer, an amplifier, a variable bandwidth filter, and a waveform synthesizer configured to synthesize a waveform at a variable frequency and provide the waveform to the mixer, wherein the receiver is configured to receive an input signal at an input, wherein the mixer, the amplifier, and the filter are disposed along a serial processing path and are configured to provide a processed signal corresponding to said input signal; a power spectral density computation module configured to generate a power spectral density of said processed signal over a selected frequency band, to provide a frequency domain signal for said frequency band, wherein the selected frequency band is variable; and a state machine configured to reconstruct, based on plural frequency domain signals provided by said power spectral density computation module for respective bands in a plurality of frequency bands, a frequency domain representation of said processed signal over a reconstruction band having a bandwidth larger than the predetermined wideband setting, and further configured to identify, based on said frequency domain representation, a spectral component corresponding to at least one cellular telephony access mode.

15. The system of claim 14 , further comprising a received signal strength indication (RSSI) module configured to measure voltage or power of said processed signal.

16. The system of claim 14 , wherein the state machine is further configured to control a bandwidth and frequency of the receiver.

17. The system of claim 16 , further comprising a received signal strength indication (RSSI) module configured to measure voltage or power of said processed signal after said receiver is controlled to a bandwidth and frequency corresponding to one of the modes.

18. The system of claim 17 , wherein said state machine is further configured to synchronize the receiver to a base station based on the frequency band associated with said one mode, if an output of said RSSI module is indicative of a voltage or power measurement exceeding a predetermined threshold.

19. A system comprising: a first receiver module and a second receiver module in a multiple input multiple output (MIMO) communications system, the first and second receiver modules configured to process a first input signal and a second input signal, respectively, each receiver module including a mixer, an amplifier, and a variable bandwidth filter disposed along a serial processing path, the first and second receiver modules configured to provide a first processed signal corresponding to said first input signal and a second processed signal corresponding to said second input signal, respectively; a power spectral density computation module configured to generate a power spectral density of said first processed signal over a selected frequency band, to provide a frequency domain signal for said frequency band, wherein the selected frequency band is variable; a received signal strength indication (RSSI) module configured to measure voltage or power of said second processed signal; and a state machine having a first input coupled to an output of said power spectral density computation module and a second input coupled to an output of said RSSI module, said state machine configured to reconstruct, based on plural frequency domain signals provided by said power spectral density computation module for respective bands in a plurality of frequency bands, a frequency domain representation of said first processed signal over a reconstruction band having a bandwidth larger than the predetermined wideband setting, and further configured to identify, based on said frequency domain representation, a spectral component corresponding to at least one cellular telephony access mode.

20. The system of claim 19 , wherein the second receiver module further comprises a waveform synthesizer configured to synthesize a waveform at a variable frequency and provide said waveform to the mixer of said second receiver module; wherein said state machine is coupled to said filter of said second receiver module and to said synthesizer of said second receiver module and is configured to control a bandwidth and frequency of said second receiver module, and said RSSI module is configured to measure the voltage or power of said processed signal after said second receiver module is controlled to a bandwidth and frequency corresponding to one of the modes.

21. The system of claim 20 , wherein said state machine is further configured to synchronize said second receiver module to a base station based on the frequency band associated with said one mode, if the output of said RSSI module is indicative of a voltage or power measurement exceeding a predetermined threshold.